A Novel Ammonia-Water Cycle for Power and Refrigeration Cogeneration

Cogeneration can improve the energy utilization efficiency significantly. In this paper, a new ammonia-water system is proposed for the cogeneration of refrigeration and power. The plant operates in a parallel combined cycle mode with an ammonia-water Rankine cycle and an ammonia refrigeration cycle, interconnected by absorption, separation and heat transfer processes. The performance was evaluated by both energy and exergy efficiencies. The influences of the key parameters, which include the rectifier operation pressure, reflux ratio and reboiler temperature, the basic working solution concentration, the cooling water temperature and the Rankine cycle turbine inlet parameters on the cycle performance, were investigated. It is found that the cycle has a good thermal performance, with energy and exergy efficiencies of 25% and 50.9%, respectively, for the base-case studied (having a maximum cycle temperature of 450°C). Comparison with the conventional separate generation of power and refrigeration having the same outputs, shows that the energy consumption of the cogeneration cycle is lower by 21.6%.